A conventional film camera has been replaced by a camera module for a portable terminal using a small solid-state imaging device such as a CCD and a CMOS, a digital still camera (DSC), a camcorder, and a PC camera (an imaging device attached to a personal computer). Such imaging devices have been reduced in size and thinned.
In keeping with this trend, miniaturization of light receiving elements such as a Charge Coupled Device (CCD) mounted on a miniaturized imaging device is progressing, but the imaging lens still occupies the largest space in the imaging device.
Therefore, the imaging lens, which forms an image of an object, at the center of the issue of compact and thin design among other elements of the imaging device.
Here, realizing a small imaging lens is not the only issue. With enhancement in performance of the light receiving element, the imaging lenses are also required to exhibit high performance. However, the compact design of the imaging lens necessarily results in a close distance to the light receiving element, which causes light to be obliquely incident on the imaging surface of the imaging device. Thereby, the condensing performance of the imaging lens is not sufficiently exhibited, and brightness of the image may drastically change from the central portion of the image to the peripheral portion of the image.
A wide-angle imaging lens is manufactured with a subject side surface of a lens disposed closest to a subject protruding, in order to realize a wide angle. When the protruding lens disposed on the surface of the imaging lens is contaminated or scratched, cannot be replaced. As a result, lens performance may be deteriorated.
In view of such a problem, it is necessary to increase the number of lenses, which may increase the volume of the imaging device.